Defining Neighborhood Boundaries for Social Measurement: Advancing Social Work Research

Article excerpt

Much of the current neighborhood-based research uses variables aggregated on administrative boundaries such as zip codes, census tracts, and block groups. However, other methods using current technological advances in geographic sciences may broaden our ability to explore the spatial concentration of neighborhood factors affecting individuals and groups. This article builds on extant neighborhood-based research methods and proposes using a geographic information system (GIS) to explore a conceptually new method of defining neighborhood boundaries for social measurement. Geospatial factors are important in the formation of neighborhoods, and a GIS can be used to define neighborhood boundaries that account for the spatial factors influencing the natural flow and pattern of neighbor interactions. Georeferenced data from the 2000 U.S. census for a midwestern city are presented to elucidate the potential aggregation problems and theoretical arguments. Moran's I statistics show that administrative boundaries may not be valid aggregate measures of neighborhoods or their effects.

KEY WORDS: geographic information system; measurement; neighborhood boundaries; neighborhood effects

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The effects of place on social outcomes have long been an interest of social work research. Much of the current neighborhood-based research uses variables aggregated on administrative boundaries such as census tracts, block groups, and zip codes to explore phenomena occurring within these geospatially bound social networks (Coulton, 2005; Coulton, Cook, & Irwin, 2004; Coulton, Korbin, Chan, & Su, 2001; Coulton, Korbin, & Su, 1999; Dietz, 2002; Grannis, 1998, 2005; Mayer & Jencks, 1989; Raudenbush & Sampson, 1999; Sampson, Morenoff, & Gannon-Rowley, 2002; Sampson & Raudenbush, 1999). Census tract- and similar-level data have a place in social work research; however, novel methods using current technological advances in geographic sciences may broaden our ability to explore the spatial concentration of neighborhood factors affecting individuals and groups.

BACKGROUND

Neighborhoods are geographically bounded groupings of households and institutions connected through structures and processes (Coulton et al., 1999). Collective attributes of neighborhoods are important to measure because of their potential to elucidate how ecological factors moderate the effects of other variables or interventions. The homological problem, hence a problem of social measurement, inherent in this approach is the assumption that aggregate data based on administratively defined neighborhoods are an accurate and adequate representation of the "true" neighborhood (Coulton, 2005; Coulton et al., 2001, 2004; Sampson et al., 2002). Approaches that disregard how individuals themselves define the neighborhoods in which they live may introduce significant measurement error (Coulton et al., 2001). In addition, misspecified boundaries result in ambiguities that "have undermined the authenticity and statistical power of community studies and biased downward the estimates of community effects" (Coulton, 2005, p. 75).

It is argued here that neighborhoods are more than a summary of attributes; they are collectives that grow out of and share an ecological context with certain geospatial boundaries. The literature on neighborhood effects points to the challenges of accurately defining neighborhood boundaries for social work research. Accurate specification of boundaries in research is necessary to meet the basic statistical and measurement principal of maximizing between-group variance and minimizing within-group variance. Inaccurately specified boundaries may lead to excessive variance within the groups (problematic heterogeneity), increased measurement error, and unreliable results. Limited between-group variance (problematic homogeneity) may show little differences across groups and yield spurious null results. …